I want to create a custom one with as few plugins as possible.

First, I have to create a theme.

The "wp-content" folder in the "WordPress" folder you created.

And inside that "themes" folder, create a folder with an appropriate name.

At a minimum, you will need "functions.php", "index.php" (or "front-page.php") and "style.css".

Fixed pages are created with "page- (slug)".